Field of the Invention
The present invention relates to an apparatus and a method.
Description of the Related Art
Recently, research on imaging of functional information of a living organism which is physiological information of the living organism is being pursued in the field of medicine. One technique for imaging functional information is photoacoustic imaging (PAI). With photoacoustic imaging, first, an object is irradiated with pulsed light from a light irradiating unit. When energy of the irradiation light propagated and diffused inside the object is absorbed by a light absorber (such as a blood vessel or skin) in the object, an acoustic wave (a photoacoustic wave) is generated due to a photoacoustic effect. A conversion element then receives the photoacoustic wave and converts the photoacoustic wave into an electrical signal (a received signal). Subsequently, an information processing apparatus analyzes the received signal to acquire a distribution of optical characteristics inside the object. Information beneficial to diagnosis and the like is obtained by converting the distribution of optical characteristics into image data and displaying the image data.
Examples of a distribution of optical characteristics include a distribution of sound pressure generated due to light absorption (a distribution of initial sound pressure) and a distribution of light absorption coefficients. In addition, by irradiating a plurality of pulsed light beams with wavelengths that differ from each other and obtaining a light absorption coefficient for each wavelength, a concentration distribution of a substance present inside the object (a distribution of values related to the concentration of a substance) is obtained. A method of obtaining a distribution of oxygen saturation in blood as a concentration distribution using a difference in light absorption spectra between deoxyhemoglobin and oxyhemoglobin is disclosed in “Technical Considerations in Quantitative Blood Oxygenation Measurement Using Photoacoustic Microscopy in Vivo”, Proc. SPIE 6086, Photons Plus Ultrasound: Imaging and Sensing 2006: The Seventh Conference on Biomedical Thermoacoustics, Optoacoustics, and Acousto-optics, 60860R (Mar. 6, 2006).
Non Patent Literature 1: “Technical Considerations in Quantitative Blood Oxygenation Measurement Using Photoacoustic Microscopy in Vivo”, Proc. SPIE 6086, Photons Plus Ultrasound: Imaging and Sensing 2006: The Seventh Conference on Biomedical Thermoacoustics, Optoacoustics, and Acousto-optics, 60860R (Mar. 6, 2006)